The term superantigen was introduced in microbiology and immunology only a decade ago. The unique feature of superantigen is that it bypasses the antigen processing mechanism and specifically binds to TCR v segment and forms a trimolecular complex along with major histocompatibility complex class II. Since its discovery, several studies have been carried out to unravel the properties of superantigens. They are implicated in the pathogenesis of diseases of bacterial, viral and fungal origin. They are also known to play a role in autoimmune diseases. Therapy for these superantigens is being worked upon. Studies have shown that intravenous gamma globulin containing specific antibodies to these superantigens inhibits the activation of T-Cells and also the cytokine production by them resulting in dramatic recovery from superantigen mediated diseases. The use of superantigen in the therapy of cancer is being explored.

Rotavirus infection among infants and young children in Chennai, South IndiaP Saravanan, S Ananthan, M AnanthasubramanianOctober-December 2004, 22(4):212-221PMID:17642741

BACKGROUND: Group A rotavirus has been recognized as the major etiologic agent of childhood gastroenteritis in infants and young children worldwide. Rapid progress towards the development of an efficacious rotavirus vaccine has warranted extensive epidemiological studies on rotavirus serotypes that cause severe disease in developing and developed countries and to monitor the emergence of newer and unusual strains in different geographical settings that could represent variants not covered by existing vaccines. METHODS: In this study, we determined the prevalence of rotavirus infection and characterised group A rotavirus in stool samples by using monoclonal antibody (MAb) based ELISA and polyacrylamide gel electrophoresis (PAGE). Stool samples were collected from 745 children of 0-3 years of age presenting to the hospital with acute diarrhea between March 1995 and August 1999. These were assayed for antigenic (group, subgroup, serotype) and genomic (viral RNA profile and VP7 and VP4 genotype) characterization by ELISA and PAGE. RESULTS: Out of 745 stool samples analysed 168 were found to be positive for rotavirus. Among these 118 could be assigned a subgroup (SG), serotype and electropherotype (E-type). The study has evidenced the predominant occurrence of strains with short E-type, SGI and serotype G2 in 66.1% of the samples. The presence of strains representing 10 different E-types and mixed genotype specificities with G2 P[4,8] and G1-G2 P[4,8] has documented the prevailing high genomic diversity of rotaviruses in this geographical area. CONCLUSION: This study has described the predominant strains of rotavirus in south India. There is a need for further detailed studies on the molecular characterization of rotaviruses which would have important implications in vaccine evaluation programmes.

Methicillin resistant Stephylococcus aureus (MRSA) infection has now become a major problem in hospitals. We present a case of postoperative infection MRSA where the primary source of the infection was found to be an abdominal mesh that was used to reinforce the abdominal wall. After one year of surgery, the patient developed wound dehiscence and discharge. MRSA was isolated from the wound, mesh, external nares, throat and axilla. Initially she was started on clindamycin and discharged from the hospital. After 5 months, patient came back to the hospital with infection at the same site. The patient was then treated with vancomycin and MRSA clearance. She responded to the treatment with complete healing of the wound and clearance of MRSA.

PURPOSE: To investigate the types and causes of non-tuberculous ocular infections and study their response to topical antibiotic therapy. METHOD: A single center, retrospective review of 18 patients with non-tuberculous mycobacterial ocular infections, seen over a 3 year period was done. Laboratory diagnosis was established by growth on blood agar, LJ medium and Ziehl-Nielsen acid fast stain. RESULTS: Out of 18 patients, six had post corneal graft infection, six had corneal ulcers, three had endogenous endophthalmitis, one had post operative endophthalmitis and two cases were of post surgical wound infection. History of trauma was reported in two cases and surgery in nine cases. M.chelonae was grown in blood agar for all patients. For corneal infections fortified genatmicin and fortified amikacin topical eye drops were given while the cases of endophthalmitis received intravitreal amikacin. Response to treatment was poor in 16 cases (88.9%). Only two cases of corneal ulcer improved after prolonged treatment. There was a misdiagnosis of Corynebacterium spp. on Gram stain in the initial cases. Majority of the isolates were sensitive to gentamicin (72.2%) followed by amikacin (44.4%). CONCLUSIONS: Early clinical recognition and prompt laboratory diagnosis together with aggressive topical antibiotic therapy may shorten morbidity and improve the clinical outcome of non-tuberculous mycobacterial ocular infection.

Extended spectrum beta-lactamase (ESBL) producing strains of Klebsiella pneumoniae have emerged as important nosocomial pathogens. The present report describes an outbreak of ESBL positive K.pneumoniae in a neonatal intensive care unit of a tertiary care center in southern India. The clinical and microbiological significance of multiresistant gram negative ESBL producers have been discussed in light of this outbreak by multi-resistant gram negative bacilli. The review also offers some practical guidance regarding infection control and therapeutic options.

-lactamases represent the most common mechanism of -lactam resistance. Extended spectrum -lactamases (ESBLs) represent a major group of -lactamses currently being identified worldwide in large numbers along with inducible AmpC -lactamases and derepressed mutants. The present study was done to detect -lactamase production in clinical isolates by rearranging routine discs used in reporting susceptibility to specifically assess ESBLs, AmpC -lactamases (both inducible and hyperproducers i.e., derepressed mutants). A total of 286 clinical isolates were studied using a novel predictor disc approximation method to detect the above mechanisms of resistance with careful use and placement of antimicrobial discs. Of the 286 isolates, 151(53%) were ESBL producers of which 131(46%) were also derepressed mutants while remaining 20(7%) were plain ESBL producers. Forty (14%) were plain derepressed mutants. Inducible AmpC -lactamase production was detected in 19(7%) of the isolates. The commonest ESBL producers were E.coli and K. pneumoniae. The high incidence of -lactamase production due to multiple mechanisms in clinical isolates is alarming and urgent action needs to be taken from both a therapeutic and infection control perspective.

The present study aimed at in vitro detection of macrolide resistant phenotypes of methicillin resistant Staphylococcus aureus (MRSA) and interpretation of susceptibility tests to guide therapy. The study included 25 MRSA strains that were resistant to erythromycin and clindamycin, 25 MRSA strains that were sensitive to both erythromycin and clindamycin and 100 MRSA isolates which displayed erythromycin resistant but clindamycin susceptible phenotype. Erythromycin and clindamycin double disc susceptibility testing was done to detect inducible clindamycin resistance. Dilution susceptibility testing for clindamycin and erythromycin alone and in combination was performed for all 150 strains. Seventy-six strains showed blunting around clindamycin disc (inducible resistance). After induction with erythromycin, minimum inhibitory concentration (MIC) of clindamycin was noticed to rise from atleast 16 to 256 g/mL in iMLSB phenotypes indicating inducible resistance. The detailed result analysis suggests the possible role of clindamycin in treatment of some of the erythromycin resistant isolates (non inducible), as there are multiplicity of resistance mechanisms and diversity of phenotypic expressions.

Beta haemolytic phenotype of group G streptococci was isolated from the pus obtained from a patient with extensive deep neck space abscess. Patient was immunocompetent and made complete recovery after surgical drainage and administration of amoxycillin with clavulanic acid, amikacin and metronidazole. To our knowledge, this is the first report of deep neck space abscess due to group G streptococci.

Two hundred and thirty-six women with previous bad obstetric history (BOH), belonging to different socio-economic groups were investigated for the presence of Toxoplasma specific antibodies (IgG/IgM) using commercial diagnostic kits. The study showed a higher percentage of IgG seropositivity in women of low socioeconomic group (LSG) compared to those of high socioeconomic group (HSG). Specific IgM positivity indicative of possible acute infection, was higher in women of HSG, emphasizing the need for educating pregnant mothers on preventive measures. However, there is a need to undertake in-depth studies to understand the significance of the presence of IgM in women with BOH.

The present study was conducted on 250 serum samples of STD clinic patients and 50 serum samples of asymptomatic women to determine seroprevalence of herpes simplex-1 and 2 (HSV-1 and 2) IgM antibodies and HIV-1 and 2 antibodies. The samples were also screened for syphilis by VDRL test and confirmed by TPHA test. Seropositivity of HSV in STD clinic patients was 44/250 (17.6%) and 12/50 (24%) in asymptomatic women. In 11/44 (25%) seropositive persons for HSV, HIV 1 and 2 antibodies were present. In 10/44 (22.7%) HSV seropositive persons, coinfection with syphilis was also present, whereas in 7/44 (15.9%) HSV seropositive persons, both HIV and syphilis were present. In the control group, coinfection with other sexually transmitted infections (STIs) was not observed.

PURPOSE: This study analyses the prevalence, demography, predisposing factors and seasonal variation of Acanthamoeba keratitis. METHODS: A retrospective review of all cases presenting with keratitis at the cornea clinic, Aravind Eye Hospital, Coimbatore, from August 1997 to July 2003, was done for screening patients with a provisional diagnosis of Acanthamoeba keratitis. Their records were further analyzed for microbiological details. Cases with culture proven Acanthamoeba keratitis were included for epidemiological analysis. RESULTS: From a total of 4519 patients who attended cornea clinic 32 (33 eyes) patients were confirmed to be positive for Acanthamoeba keratitis. Twenty cases (62.5%) were males. Majority (18; 54.2%) of the Acanthamoeba keratitis eyes reported corneal trauma by solid objects. No peak period was observed in a year, as the number of cases was almost uniform in all months. CONCLUSION: This study indicates the increasing prevalence of Acanthamoeba keratitis among non-contact lens users in this region during the 6-year period.

Onycholysis caused by Candida krusei is rare. A 21 years old male patient presented with grayish discolouration and elevation of all fingernails since one year. Patient was refractory to treatment with fluconazole. Potassium hydroxide preparation of subungual debris revealed fungal elements. Growth on Sabouraud dextrose agar was identified by cultural characteristics, morphotyping, microscopy and biochemical tests as Candida krusei. The isolate was resistant to fluconazole and amphotericin-B but susceptible to nystatin and clotrimazole. Patient responded well to clotrimazole and terbinafine.

DNA fingerprinting using IS 6110 probe has been used all over the world quite successfully to characterize M. tuberculosis strains. The present study has been carried out to study the polymorphism among isolates of M.tuberculosis from Agra region from patients attending the clinics at SN Medical College and TBDTC, Agra. Sputa were collected in sterilized containers and brought to CJIL, Agra. Samples were processed and cultured on Lowenstein Jensen (LJ) slants. M. tuberculosis isolates were identified by standard biochemical tests. DNA from these isolates were purified by a physicochemical procedure, restricted with Pvu II enzyme and hybridized with PCR amplified and DIG labeled 245 bp IS 6110 probe. With a view to study IS 6110 polymorphism, M. tuberculosis isolates obtained from different geographical areas of Agra region were analyzed. Among the 60 isolates taken in study, 5 had no copy of IS 6110, 8 had 1-4 copies and 47 had multiple copies of IS 6110. DNA fingerprinting using this probe was found to be quite discriminating for typing of most of the strains (80%) which had multiple copies. RFLP profiles did not correlate with geographical areas, contacts or the resistance pattern of the strains. While this data shows the potential of IS 6110 based RFLP for strain characterization of M.tuberculosis in Agra, to understand the molecular epidemiology of tuberculosis in this region, a larger number of isolates from defined geographical areas need to be studied.

Burkholderia pseudomallei, a natural saprophyte widely distributed in soil, stagnant waters of endemic areas, is said to infect humans through breaks in the skin or through inhalation causing protean clinical manifestations including fatal septicaemia. A case of septicaemia in a elderly female diabetic due to B. pseudomallei following a history of fall is being reported with complete details.

PURPOSE: The study was carried out to test the in vitro activity of gatifloxacin (GT) against the commonly isolated gram negative pathogens from clinical specimens and compare the same with that of two other fluoroquinolones-ciprofloxacin (CIP) and levofloxacin (LVX) and four non-quinolone agents- cefotaxime (CF), ceftriaxone (CTX), ceftazidime (CAZ) and amoxyclav (AMC). The study included 77 gram negative isolates. METHODS: The in vitro activity of gatifloxacin was evaluated by the Kirby-Bauer disc diffusion method and the MIC was determined by the agar dilution method as per the NCCLS guidelines. RESULTS: Of the organisms tested, 62.8% of the isolates belonging to the family Enterobacteriaceae were sensitive to GT, compared to 36.1 to LVX, 27.8 to CIP, 41.61 to AMC and 32.2% to the cephalosporins tested. For P.aeruginosa, the figures were 41.2, 41.2, 23.5 and 35.3% for GT, CIP, LVX, and the III generation cephalosporins, respectively. CONCLUSION: Gatifloxacin was more effective than the other two fluoroquinolones and the non-quinolone antibiotics against the members of Enterobacteriaceae. However, GT and CIP were found to be equally effective against P.aeruginosa.